Higher intake of folate and vitamin B6 above the recommended daily amount did not reduce Parkinson disease (PD) risk. Although intake of vitamin B12 early in life was linked to a decreased risk for PD, the findings were inconsistent. These are the results of a study published in the journal Movement Disorders.
Current treatment for PD is aimed at managing symptoms, as they do not stop or slow the progression of the disease. B vitamins and folate have been proposed as preventative factors in the development of PD, as they demonstrate decreased neurotoxic homocysteine levels and exhibit antioxidant effects. For the study, researchers aimed to investigate these claims and provide an association between the long-term intake of folate, vitamin B6, and vitamin B12 and their utility in preventing or delaying the onset of PD.
The researchers conducted a 30-year prospective study using a cohort gathered from the Nurses’ Health Study (NHS) and the Health Professionals Follow-up Study (HPFS). The NHS and HPFS comprised 80,965 women and 48,837 men, respectively.
Nutritional data were evaluated using a food frequency questionnaire (FFQ) which was administered to both cohorts. Values of folate, vitamin B6, and vitamin B12 were quantified using information gathered from the U.S. Department of Agriculture (USDA). Data were stratified into quintiles of increasing intake and adjusted for various parameters including body mass index (BMI), smoking, physical activity, alcohol and caffeine intake, and total energy intake. Exclusion criteria consisted of participants with a diagnosis of PD or those who have missing dietary information, as well as those who have not submitted complete FFQs.
The primary outcome of the study was the incidence of PD, identified by self-reporting questionnaires and then confirmed with follow-up with the treating neurologists or a medical record indicating at least 2 of the 3 principal signs of PD (tremor, rigidity, akinesia, or bradykinesia).
In analyzing both studies of a pooled cohort of 129,982 individuals, 1426 new cases of PD were identified (687 women, 739 men). No association was found between total folate intake and incident PD; pooled hazard ratio (HR) relating to the top and bottom quintile of intake was 1.15 (95% CI, 0.95-1.40; P-trend =.41).
Vitamin B6 intake was not associated with the risk for PD, however, an analysis with a 20-year lag found higher intake was associated with a lower risk for PD. This association was stronger in women and in individuals who had intake from dietary sources (HR comparing top vs bottom dietary intake in women = 0.64; 95% CI, 0.44-0.93; P-trend =.02). However, baseline intake of vitamin B6 or intake during specific time periods was associated with PD risk.
The cumulative average intake of vitamin B12 was not associated with PD risk. Notably, a moderate inverse association was found for baseline total B12 with a pooled HR of 0.80 (95% CI, 0.67-0.95; P-trend =.01), which compared the top and bottom quintiles of intake. This relation was found only when accounting for dietary and supplemental sources of vitamin B12; when excluding supplement intake at baseline, no association was observed.
Additionally, no effect modification was found when adjusting for alcohol intake (<15 vs ≥15 g per day), baseline age, or smoking status.
Study limitations included self-reported intakes of vitamins compared with documented intakes or blood levels of vitamins. Lack of generalizability is also possible as the study population comprised individuals who were White, well-educated, and adequately nourished.
The researchers concluded, “The results of this large prospective study do not support the hypothesis that increasing folate or vitamin B6 intakes above the current levels would reduce PD risk in this population of mostly white U.S. health professionals. For vitamin B12, a decreased PD risk was observed among individuals in the highest quintile of intake in some of our analyses, leaving open the possibility of a protective effect of vitamin B12 on the development of PD.”
Flores-Torres MH, Christine CW, Bjornevik K, et al. Long-term intake of folate, vitamin B6, and vitamin B12 and the incidence of Parkinson’s disease in a sample of U.S. women and men. Published online March 20, 2023. Mov Disord. https://doi.org/10.1002/mds.29383